1. Field of Invention
The invention relates to an overvoltage protection device for protection of an electrical or electronic device, with a housing, with input and output terminals for electrical conductors, with line paths each of which connect an input terminal to an output terminal, with first arresters which are used for symmetrical protection between the active conductors and with second arresters which are used for asymmetrical protection between the individual conductors and the ground potential, the individual first arresters each being connected by their first terminal to a line path and by their second terminal to a common connecting point so that they are at a common reference potential and symmetrical protection between two conductors is implemented by two first arresters located in series to one another. In addition, the invention relates to an overvoltage protection arrangement having at least two overvoltage protection devices.
2. Description of Related Art
Interfaces in the field of measurement, control and feedback technology are far more sensitive to overvoltages than power supply systems. Sensitivity has increased to the degree to which the use of electronic components, especially transistors and thyristors in electrical devices, installation and systems has increased. Mainly, the integrated circuits used increasingly in electrical and electronic devices are greatly endangered by transient overvoltages.
Electrical circuits and electrical devices normally work without problems using the voltage specified for them, the rated voltage. This does not apply when overvoltages occur. Overvoltages are considered to be all voltages which are above the upper tolerance limit of the rated voltage. They also include mainly transient overvoltages which can occur due to atmospheric discharges, but also due to switching operations or short circuits in power supply grids, and can be metallically, inductively or capacitively coupled into electronic circuits. In order to protect electrical or electronic circuits, especially in measurement, control and feedback technology, against transient overvoltages, overvoltage protection elements have been developed which capture or limit overvoltage peaks. They are installed generally directly upstream of the signal inputs to be protected, in order to prevent the danger of overvoltage coupling on the line path between the overvoltage protection device and signal inputs of the devices.
In electrical and electronic devices, generally, the dielectric strength of the individual lines is distinctly higher relative to ground than between the individual active lines. Moreover, since the disturbances originating from the ground potential are generally of higher energy than coupled disturbances between the lines, overvoltage protection devices for protection of electrical or electronic devices often have two different types of arresters. The first arresters are used for symmetrical protection between the active conductors and the second arresters are used for asymmetrical protection between the individual conductors and the ground potential. The arresters for symmetrical protection are generally fine protection elements, especially suppressor diodes, which are characterized by short response times in the ms range and by low limiting voltages. The arresters for asymmetrical protection are conversely often gas-filled overvoltage arresters which have high discharge capacity.
These overvoltage protection devices for the field of measurement, control and feedback technology have been sold for many years by the applicant under product names “PLUGTRAB” (compare Phoenix Contact Prospectus “Overvoltage protection TRABTECH 2007, pages 60 ff). The known overvoltage protection devices are made especially as 2-channel or 4-channel devices to which two or four signal conductors can be connected so that with them symmetrical protection only between a maximum of four signal conductors can be ensured.